DIY SOS!

Folks - I've spent the last 3 days constructing my roll-off shed. I thought I might get it done in two days and I reckon I'm only about half way there!

Anyway, my dilema is this. I have constructed the walls and roof of the beast with a batten-frame (bits of wood). Around the frame, I've put a plastic skin (damp proof membrane).

Over the plastic skin I've put tongue-and-groove planks which I now want to seal (by painting them). I bought some heavy-duty looking preservative but on reading the small-print, it says not to have it anywhere near plastic... So, I don't want to see my DPM dissolve before my eyes.

So, can anyone suggest a good weather sealent that's not solvent based?

By the way, the roof will be felted, so its only the walls I need to do.

Appreciate it.

Dave McD

Hey Dave,

If you can live with the poor choice of colours, floor paint is a good all rounder. It's polymer based so it shouldn't interfere with your plastic membrane and it sets quite nicely. Good for about 5 years.

However, this is the nuclear option as the finish isn't as nice.. If you can tell me what kind of plastic the membrane is made (look out for recycle symbol, PE, PET, PVC etc.) from I should be able to tell you if it will react to a thinner or not. Alternatively, you could just test a small area to see if one disolves the other. Make sure you test it in a well ventilated area, they can form some pretty nasty gases.

You could also use a polymer based varnish.

That's my 2c worth.
Dave P

Cheers Dave - I'd rather use something designed for outdoors - you know, fence paint or similar. Though paint is probably a bad description - more like a staining fluid - but with preservatives and fungicides etc.

Varnish fills me with dread...

PIFA DPM is the name of the stuff - damp-proof membrane is the DPM bit if that helps.

I was going to test the Cuprinol stuff I bought but I figured if I broke the seal, I couldn't exchange it. And if I remember, it was about 20 quid for 5 litres. Better find the receipt....

Cheers

Dave

Hi Dave,

Is your DPM that heavy blue plastic stuff? If it is it's probably HDPE, High Density Polyethylene- see if you can see HDPE printed anywhere. HDPE has limited reaction with solvents- check your cuprinol for benzene, toluene, xylene and solvents such as chloroform, methylene chloride and trichloroethylene.
These solvents cause some degree of solvation but even then the temperature would want to increase to about 80C to do any real damage. No known solvents can dissolve HDPE at room temperature.
If your not sure your DPM is HDPE check the manufacturers website.

And don't knock the floor paint -it's been on my brothers boat and shed for the past 5 years without any degredation. It's good stuff!

Cheers,
Dave P

Hi Dave - no sign of HDPE on the sheeting but it IS really heavy blue plastic for sure.

I threw away the label on the roll unfortunately...

All it says on the tin is 'contains petroleum bitumen' and 'high in VOC's'

I might just use it anyway - if it degrades the plastic, I'll use it on the fence...

Cheers!

Dave

Petroleum bitumen is a solvent- should be no prob there. VOC's are Volatile Organic Compounds- they are just warning you about the fumes! The good news is that with most solvents the nasties evaporate quickly (into the atmosphere-not so good for mother nature). My gut says go for it- I'm pretty certain your plastic is HDPE, or at least LDPE. It would want to be a very low grade polyethylene to degrade- like recycled PE.